TWI685520B - Polyester film and electrical insulating sheet, wind generator, adhesive tape, and manufacturing method of polyester film using the same - Google Patents

Abstract

A polyester film comprising a layer (P layer) of a polyester film, the layer (P layer) containing crystalline polyester (A) and plate-like particles (b1) with an aspect ratio of 2 or more and an aspect ratio of 2 or more At least one of the acicular particles (b2) has a Young's modulus of 2 GPa or more, and the plate-like particles (b1) having an aspect ratio of 2 or more and acicular particles (b2) having an aspect ratio of 2 or more contained in the P layer When the sum of the contents is regarded as Wb (mass %), and the porosity in the P layer is regarded as V (vol%), Wb is 10 or more, and V/Wb is 1 or less.

The present invention provides a polyester film excellent in electrical insulation, thermal conductivity, and mechanical properties. Furthermore, by using such a polyester film, it is possible to provide an electrical insulating sheet excellent in high thermal conductivity, an adhesive tape, and a wind power generator and electronic equipment using the same.

Description

Polyester film and electrical insulating sheet, wind generator, adhesive tape, and manufacturing method of polyester film using the same

The present invention relates to polyester films. In addition, the use of the film of electrical insulation sheet, wind generator or adhesive tape.

Polyester (especially polyethylene terephthalate or polyethylene 2,6-naphthalene dicarboxylate, etc.) resins have excellent mechanical properties, thermal properties, chemical resistance, electrical properties, and moldability, and are used in various Various uses. The polyester film made of polyester film, especially the biaxially oriented polyester film, can be used as a copper-clad laminate, a back sheet for solar cells, an adhesive tape, and flexibility based on its mechanical properties, electrical properties, etc. Printed circuit boards, membrane switches, planar heating elements, electrical insulation materials such as flat cables, motor insulation materials, magnetic recording materials, or capacitor materials, packaging materials, automotive materials, construction materials, photographic applications, drawing applications, It is used for various industrial materials such as thermal transfer applications.

In these applications, the electrical insulation materials used in motors (such as insulation sheets for wind power generation, hybrid motors, air conditioning motors), etc., due to the miniaturization and high density of motors, etc. Heat generation occurs during power generation or use, or this heat accumulates and the temperature rises, and there is a problem that the power generation efficiency is reduced or the power consumption becomes high. Similarly, in solar cell backsheet materials, etc., the temperature rises due to heat accumulation during power generation , There is a problem of lower power generation efficiency. Therefore, it is important to make the heat generated inside and conduct heat to the outside. In addition, in the electrical insulating materials used for electronic parts (for example, adhesive tapes for electronic parts, flexible printed boards, membrane switches, etc.), due to the recent high-performance, miniaturization, and high integration of electronic parts As a result, various electronic components have increased heat generation, reduced processing speed, or increased power consumption. Therefore, it is important to dissipate the heat generated inside to the outside through the housing.

Therefore, a thin film with high thermal conductivity is required, and various materials have been proposed. For example, a composite film in which a protective layer of a PET film is laminated on one side or both surfaces of a graphite sheet with high thermal conductivity (Patent Document 1), and a film containing a fibrous carbon material in biaxially stretched PET (Patent Document 2) , Patent Document 3), etc.

[Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2008-80672

Patent Document 2: Japanese Patent Laid-Open No. 2013-28753

Patent Document 3: Japanese Patent Laid-Open No. 2013-38179

However, in the technique of Patent Document 1, the graphite sheet is brittle and lacks mechanical properties. The PET film used as the protective layer has a low thermal conductivity, and there is a problem that the high thermal conductivity of the graphite film cannot be fully utilized, and the thickness becomes thick. In addition, the technologies of Patent Document 2 and Patent Document 3 cannot be used for applications requiring insulation due to their electrical conductivity. Up to insulating materials or solar cell backplanes, electronic parts, etc.

Therefore, the subject of the present invention is to provide a polyester film excellent in electrical insulation, thermal conductivity, and mechanical properties.

In order to solve the above problems, the present invention adopts the following configuration. which is,

(1) A polyester film comprising a layer (P layer), the layer (P layer) containing a crystalline polyester (A), and plate-like particles (b1) having an aspect ratio of 2 or more and an aspect ratio At least one of the acicular particles (b2) of 2 or more, having a Young's modulus of 2 GPa or more, and the plate-like particles (b1) with an aspect ratio of 2 or more and acicular particles with an aspect ratio of 2 or more contained in the P layer When the sum of the contents of (b2) is Wb (mass %), and the porosity in the P layer is V (volume %), Wb is 10 or more and V/Wb is 1 or less.

(2) The polyester film according to (1), wherein the plate-like particles (b1) having an aspect ratio of 2 or more and the needle-like particles (b2) having an aspect ratio of 2 or more have a surface with a crystalline polyester (A ) Has a reactive substituent (hereinafter referred to as a reactive substituent (a)), the amount of the reactive substituent (a) per unit surface area of the particle (B) is 0.2×10 ^-6 mol/m ² Above 1.4×10 ^-4 mol/m ² or less.

(3) The polyester film according to (1) or (2), wherein the P layer contains any one of plate-like particles (b1) with an aspect ratio of 2 or more and needle-like particles (b2) with an aspect ratio of 2 or more, When the content of the plate-like particles (b1) with an aspect ratio of 2 or more contained in the P layer is regarded as Wb1 (mass %), and the content of the acicular particles (b2) with an aspect ratio of 2 or more is regarded as Wb2 (mass %) , Wb2/Wb1 is 0.7 or more and 9 or less.

(4) The polyester film described in any one of (1) to (3) has a breaking elongation of 10% or more.

(5) The polyester film according to any one of (1) to (4), wherein the difference ΔTcg between the glass transition temperature Tg of the P layer and the cold crystallization peak top temperature Tcc of the P layer is 44°C or more.

(6) The polyester film according to (1) to (5), which has a dynamic storage elastic modulus E′ of 100° C. obtained by dynamic viscoelasticity measurement at a frequency of 1 Hz (hereinafter referred to as DMA) of 5 ×10 ⁷ Pa or more.

(7) The polyester film according to any one of (1) to (6), the thermal conductivity in the film thickness direction is 0.15 W/mK or more, and the surface specific resistance is 10 ¹³ Ω/□ or more.

(8) An electrically insulating sheet formed using the polyester film as described in any one of (1) to (7).

(9) A wind power generator, which is formed using the electrical insulation sheet as described in (8).

(10) An adhesive tape made of the polyester film as described in any one of (1) to (7).

(11) A method of manufacturing a polyester film as described in any one of (1) to (7), characterized in that it comprises, in order: a crystalline polyester (A) and a polycrystalline compound on the surface The ester (A) has a reactive substituent (hereinafter referred to as a reactive substituent (a)) and a plate-like particle (b1) having an aspect ratio of 2 or more, and has a reactive substituent (a) on the surface and an aspect ratio At least one of the needle-like particles (b2) or more is subjected to a step of melt-kneading (hereinafter referred to as a melt-kneading step) to melt the resin composition containing the crystalline polyester (A) and the aforementioned particles and discharge it from the nozzle And get the film Step (hereinafter, described as a melt extrusion step), a step of biaxially stretching the film (hereinafter, described as a stretching step).

(12) The method for producing a polyester film as described in (11), wherein the plate-like particles (b1) having an aspect ratio of 2 or more and the needle-like particles (b2) having an aspect ratio of 2 or more have a reactive substituent per unit surface area The amount of (a) is 0.2×10 ⁻⁶ mol/m ² or more and 1.4×10 ⁻⁴ mol/m ² or less.

(13) The method for producing a polyester film according to (11) or (12), wherein the plate-like particles (b1) having an aspect ratio of 2 or more and the needle-like particles (b2) having an aspect ratio of 2 or more are reactive When the surface treatment agent of the substituent (a) treats the mass of the particles (B) as 100 parts by mass, the mass ratio of the surface treatment agent is 0.1 parts by mass or more and 5 parts by mass or less.

(14) The method for producing a polyester film as described in any one of (11) to (13), wherein after obtaining a fragment-like composition in the melt-kneading step, the resulting fragments are solid-phase polymerized and then melt-extruded Steps are taken to melt film formation.

According to the present invention, it is possible to provide a polyester film having better electrical insulation, thermal conductivity and mechanical properties than conventional polyester films. The polyester film is suitable for electrical insulation materials such as copper-clad laminates, solar cell back sheets, adhesive tapes, flexible printed circuit boards, membrane switches, planar heating elements, flat cables, etc. Materials, automotive materials, and construction materials represent applications that value electrical insulation and thermal conductivity. In particular, by using the polyester film, it is possible to provide a wind generator with high power generation efficiency, a solar cell, and an electronic device with low power consumption.

1‧‧‧Length (l)

2‧‧‧Width (b)

3‧‧‧Thickness (t)

Fig. 1 is a diagram schematically showing an example in which particles are surrounded by circumscribed cuboids.

[Forms for carrying out the invention]

The polyester film of the present invention must have a layer (P layer) including crystalline polyester (A) and plate-like particles (b1) with an aspect ratio of 2 or more and needle-like particles with an aspect ratio of 2 or more ( At least one kind of particles in b2) (hereinafter, plate-like particles (b1) with an aspect ratio of 2 or more and needle-shaped particles (b2) with an aspect ratio of 2 or more are also collectively referred to as particles (B)).

In the polyester film of the present invention, the crystalline polyester (A) is a polyester composed mainly of a dicarboxylic acid component and a glycol component, and is based on JIS K-7122 (1987). 20℃/min heating rate, heating the resin from 25℃ to 300℃ (1stRUN), after holding in this state for 5 minutes, then quenching until it becomes 25℃ or less, and then from room temperature to 20℃/min again The temperature is increased to 300°C. In the obtained 2ndRUN differential scanning calorimetry chart, the heat of crystallization melting ΔHm obtained from the peak area of the melting peak is 15 J/g or more. A resin with a heat of crystallization melting △Hm of more preferably 20 J/g or more, particularly preferably 25 J/g or more, and particularly preferably 30 J/g or more can be used. As the polyester constituting the P layer, by using the crystalline polyester (A), in the production method described later, alignment/crystallization is easy, and a high heat-resistant film can be obtained. In addition, in this specification, the so-called component means the smallest unit that can be obtained by hydrolyzing polyester.

烯二羧酸、異山梨醇、環己烷二羧酸、十氫萘二羧酸等之脂環族二羧酸、對苯二甲酸、間苯二甲酸、苯二甲酸、1,4-萘二羧酸、1,5-萘二羧酸、2,6-萘二羧酸、1,8-萘二羧酸、4,4’-二苯基二羧酸、4,4’-二苯基醚二羧酸、5-鈉磺酸基間苯二甲酸、蒽二羧酸、菲二羧酸、9,9’-雙(4-羧基苯基)茀酸等之芳香族二羧酸、或其酯衍生物，惟不受此等所限定。又，亦可採用於上述的羧酸構成成分之羧基末端，附加有1-丙交酯、d-丙交酯、羥基苯甲酸等之含氧酸類、及其衍生物、或含氧酸類連接複數個者等。又，此等係可單獨使用，按照需要也可使用複數種類。 Examples of the dicarboxylic acid constituting the polyester include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, and Aliphatic dicarboxylic acids such as adipic acid, pimelic acid, azelaic acid, methylmalonic acid, ethylmalonic acid, adamantane dicarboxylic acid,

Alicyclic dicarboxylic acids such as olefin dicarboxylic acid, isosorbide, cyclohexane dicarboxylic acid, decahydronaphthalene dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene Dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 1,8-naphthalene dicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl Aromatic dicarboxylic acids such as diethyl ether dicarboxylic acid, 5-sodium sulfoisophthalic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, 9,9'-bis(4-carboxyphenyl) stilbonic acid, Or its ester derivatives, but not limited by these. In addition, oxygenated acids such as 1-lactide, d-lactide, and hydroxybenzoic acid, derivatives thereof, or oxygenated acids may be added to the carboxy terminus of the above-mentioned carboxylic acid constituents. Etc. In addition, these systems can be used alone, or plural types can be used as required.

In addition, as a diol constituent component constituting the polyester, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1, Aliphatic diols such as 3-butanediol, cyclohexanedimethanol, spiroglycol, isosorbide and other alicyclic diols, bisphenol A, 1,3-benzenedimethanol, 1, The diols such as 4-benzenedimethanol, 9,9'-bis(4-hydroxyphenyl) stilbene, aromatic diols, etc., and the plurality of diols mentioned above are examples, but not limited to these . In addition, these systems can be used alone, or plural types can be used as required.

In addition, in the polyester film of the present invention, the proportion of the aromatic dicarboxylic acid constituent component in all the dicarboxylic acid constituent components in the crystalline polyester (A) in the P layer is preferably 90 mole% or more 100 Moore% below, more It is preferably 95 mol% or more and 100 mol% or less, particularly preferably 98 mol% or more and 100 mol% or less, particularly preferably 99 mol% or more and 100 mol% or less, and most preferably 100 mol%, ie All dicarboxylic acid constituent components may be aromatic carboxylic acid constituent components. If it is less than 90 mol%, the heat resistance may be reduced. In the polyester film of the present invention, by setting the proportion of the aromatic dicarboxylic acid constituent component in all the dicarboxylic acid constituent components in the crystalline polyester (A) in the P layer to be 90 mole% or more and 100 mole The ear% or less, in the manufacturing method described later, alignment/crystallization becomes easy, and a high heat-resistant thin film can be formed.

In the polyester film of the present invention, the repeating unit of the crystalline polyester (A) of the P layer, that is, the main repeating unit composed of the dicarboxylic acid component and the diol component, is preferably made of terephthalic acid. Ethylene glycol, ethylene 2,6-naphthalene dicarboxylate, propylene terephthalate, butylene terephthalate, 1,4-cyclohexyldimethylene terephthalate, 2 , 6-naphthalenedicarboxylic acid ethylene glycol esters, it is preferred that these become the main repeating unit. Furthermore, the main repeating unit mentioned here is that the total of the above repeating units is 80 mol% or more of all the repeating units, more preferably 90 mol% or more, and particularly preferably 95 mol% or more.

In addition, from the viewpoint of low cost, easier polymerization, and excellent heat resistance, it is preferable that ethylene terephthalate and ethylene 2,6-naphthalene dicarboxylate are the main repeating units. In this case, when ethylene terephthalate is used as the main repeating unit, a versatile and heat-resistant film can be obtained inexpensively, and when ethylene 2,6-naphthalene dicarboxylate is used as the main repeating unit, It becomes a film with more excellent heat resistance.

By suitably combining the above constituent components (dicarboxylic acid and diol) and condensing the poly, polyester can be obtained, but in the polyester film of the present invention, P It is also preferable that the crystalline polyester (A) of the layer is a copolymerized component having 3 or more carboxyl groups and/or hydroxyl groups. In this case, the copolymerization rate of the constituent components having three or more carboxyl groups and/or hydroxyl groups is preferably 0.005 mol% or more and 2.5 mol% or less with respect to all the constituent components of the crystalline polyester (A).

In the polyester film of the present invention, the intrinsic viscosity (hereinafter referred to as IV) of the crystalline polyester (A) constituting the P layer is preferably 0.6 or more, more preferably 0.65 or more, particularly preferably 0.68 or more, and particularly preferably It is 0.7 or more. If the IV is small, when the particles (B) described later are included, the inter-molecular complexation becomes too small, mechanical properties cannot be obtained, or the mechanical properties deteriorate with time, which is easy to proceed or may be brittle. . In the polyester film of the present invention, by setting the IV of the crystalline polyester constituting the P layer to 0.6 or more, high mechanical properties can be obtained. In addition, the upper limit of IV is not specifically defined, but it may be disadvantageous in terms of cost due to the long polymerization time, or it may be difficult to melt extrusion. Therefore, it is preferably 1.0 or less, and more preferably 0.9 or less.

In addition, in order to obtain the above-mentioned IV polyester, there is a method of discharging, stranding, cutting, and fragmenting at a time when the melt viscosity becomes a predetermined melt viscosity, by using a lower than target Intrinsic viscosity is temporarily fragmented, and then obtained by solid-phase polymerization. Among these, especially when the IV is 0.65 or more, from the viewpoint of suppressing thermal degradation and reducing the number of carboxyl terminal groups, it is preferable to temporarily fragment with a lower inherent viscosity than the target, and then perform the solid phase The method of polymerization. More preferably, after the particles (B) are contained in the crystalline polyester (A) by the method described later, the solid-phase polymerization is performed to further increase the IV of the film. As a result, when the particles (B) are contained in the crystalline polyester (A) and the film is formed by the manufacturing method described later, excessive crystallization can be suppressed and the stretchability Increased, the mechanical properties of the resulting film increased.

In the polyester film of the present invention, the melting point Tm of the crystalline polyester (A) constituting the P layer is preferably 240° C. or higher and 290° C. or lower. The melting point Tm mentioned here is the melting point Tm obtained by DSC in the temperature rising process (heating rate: 20°C/min), by a method according to JIS K-7121 (1987), from 25°C to polyester The melting point of +50°C is heated at a heating rate of 20°C/min (1stRUN), held in this state for 5 minutes, then quenched to below 25°C, and then heated from room temperature to 20°C/min. Up to 300°C, the melting point Tm of the crystalline polyester (A) is taken as the peak top temperature of the crystal melting peak of the obtained 2ndRun. The melting point Tm is more preferably 245°C or higher and 275°C or lower, and particularly preferably 250°C or higher and 265°C or lower. If the melting point Tm is less than 240°C, the heat resistance of the film will be unfavorable, and if the melting point Tm exceeds 290°C, extrusion processing will be difficult and unfavorable. In the polyester film of the present invention, by setting the melting point Tm of the crystalline polyester (A) constituting the P layer to 245° C. or higher and 290° C. or lower, a polyester film having heat resistance can be formed.

唑啉基、環氧基、碳二亞胺基、異氰酸酯基等的取代基之化合物等。使用耐水解劑時，相對於P層，較佳為含有0.01質量%以上。更佳為0.1質量%以上。藉由與上述聚酯組合，添加耐水解劑，可抑制因粒子添加所致的聚酯之劣化，可進一步提高機械特性、耐熱性。再者，從過剩的耐水解劑會使難燃性降低之觀點來看，相對於P層，耐水解劑之含量的上限較佳為2質量%以下，更佳為1質量%以下，尤佳為0.8%質量%以下。 In the polyester film of the present invention, the number of carboxyl terminal groups of the crystalline polyester (A) constituting the P layer is preferably 40 equivalents/t or less, more preferably 30 equivalents/t or less, and particularly preferably 20 equivalents/t or less . If the number of carboxyl terminal groups is high, even if the structure is controlled, the protons derived from the carboxyl terminal groups have a strong catalytic action, promote hydrolysis or thermal decomposition, and the deterioration of the ordinary polyester film may be more likely to proceed. By setting the number of carboxyl terminal groups within the above-mentioned range, a polyester film with suppressed deterioration such as hydrolysis or thermal decomposition can be formed. Furthermore, in order to make the number of carboxyl terminal groups equal to or less than 40 equivalents/t, it can be obtained by using the polyester obtained as follows: (1) The esterification reaction of the dicarboxylic acid component and the diol component is carried out by melting When the polymerization becomes a predetermined melt viscosity, discharge, stranding, cutting, and after fragmentation, solid phase polymerization method, (2) From the end of the transesterification reaction or esterification reaction to the beginning of the polycondensation reaction (Intrinsic viscosity is less than 0.3) The combination of methods such as adding buffers etc. In addition, it can also be obtained by adding a buffering agent or an end blocking agent during molding. The term “terminal blocking agent” refers to a compound that reacts with a carboxyl terminal group or a hydroxyl terminal group of a polyester to bond, so that the catalytic activity of a proton derived from the terminal group disappears. Specifically, the compound has

Compounds of substituents such as oxazoline group, epoxy group, carbodiimide group, isocyanate group, etc. When a hydrolysis-resistant agent is used, it is preferably contained at 0.01% by mass or more relative to the P layer. More preferably, it is 0.1 mass% or more. By combining with the above-mentioned polyester and adding a hydrolysis-resistant agent, the deterioration of the polyester due to the addition of particles can be suppressed, and the mechanical properties and heat resistance can be further improved. In addition, from the viewpoint of excessive flame retardant reducing flame retardancy, the upper limit of the content of the hydrolytic agent relative to the P layer is preferably 2% by mass or less, more preferably 1% by mass or less, particularly preferably It is 0.8% by mass or less.

The polyester film of the present invention must contain at least one kind of plate-like particles (b1) with an aspect ratio of 2 or more and needle-like particles (b2) with an aspect ratio of 2 or more in the P layer (hereinafter, a plate with an aspect ratio of 2 or more The shaped particles (b1) and the needle-shaped particles (b2) having an aspect ratio of 2 or more are collectively referred to as particles (B)). The plate-like particles (b1) with an aspect ratio of 2 or more mentioned here are the primary particles surrounded by an circumscribed cuboid as shown in Figure 1, the longest side of the circumscribed cuboid is defined as the length (l), and the shortest side When defined as the thickness (t) and the remaining side as the width (b), the ratio of the length (l) to the thickness (t) l/t is 2 or more, and the ratio of the length (l) to the width (b) l /b is 1 to 2 particles. In addition, the needle-shaped particles (b2) with an aspect ratio of 2 or more are surrounded by primary particles surrounded by a circumscribed cuboid as shown in Figure 1, and the longest side of the circumscribed cuboid is defined as the length (l), and the shortest One side is defined as the thickness (t), and the remaining side is defined as the width (b), the ratio of the length (l) and the thickness (t) l/t is 2 or more, and the length (l) and the width (b) Particles with a ratio l/b greater than 2. In addition, the aspect ratio mentioned here is the ratio l/t of the length (l) and thickness (t) of the plate-like particles or needle-like particles. The contact probability between the polyester film-based particles containing plate-like particles or needle-like particles with an aspect ratio of 2 or more is higher than that of spherical particles, and the higher the aspect ratio, the higher the contact probability. Therefore, in the polyester film of the present invention, the sum of the contents (Wb) of the plate-like particles (b1) having an aspect ratio of 2 or more and the acicular particles (b2) having an aspect ratio of 2 or more becomes 10% by mass or more The P layer contains particles to provide thermal conductivity to the polyester film. The aspect ratio is more preferably 3 or more, and particularly preferably 5 or more. In addition, the upper limit of the aspect ratio is not specifically defined, but from the viewpoint of preventing the particles from being bent or broken when the particles (B) are kneaded into the resin, it is preferably 40 or less, and more preferably 30 or less.

The sum of the contents of the plate-like particles (b1) with an aspect ratio of 2 or more and the needle-like particles (b2) with an aspect ratio of 2 or more contained in the P layer must be 10% by mass or more, more preferably 12% by mass More than 50% by mass or less, particularly preferably 15% by mass or more and 40% by mass or less, and particularly preferably 18% by mass or more and 35% by mass or less. If the content is less than 10% by mass, the probability of contact between particles becomes low, and as a result, the thermal conductivity decreases. If the content exceeds 50% by mass, the film formability of the film or the mechanical properties after stretching will decrease.

In the polyester film of the present invention, the length (l) of the plate-like particles (b1) and the needle-like particles (b2) is preferably 1 μm or more and 80 μm or less, more preferably 2 μm or more and 40 μm or less, particularly preferably 3 μm or more and 20 μm or less. If the length (l) is less than 1 μm, the interface area may become too large and the thermal conductivity may be reduced. If it exceeds 80 μm, the film formability of the thin film may be reduced. In particular, the elongation in the stretching step described later may be reduced and productivity may be deteriorated. Situation. In the polyester film of the present invention, by setting the lengths of the plate-like particles (b1) and the needle-like particles (b2) to 1 μm or more and 80 μm or less, the thermal conductivity and the film-forming property can coexist.

In the polyester film of the present invention, materials of plate-like particles (b1) and needle-like particles (b2) that can be used include, for example, gold, silver, copper, platinum, palladium, rhenium, vanadium, osmium, cobalt, and iron , Zinc, ruthenium, magnesium, chromium, nickel, aluminum, tin, titanium, tantalum, zirconium, antimony, indium, yttrium, lanthanum and other metals, zinc oxide, titanium oxide, cesium oxide, antimony oxide, tin oxide, indium tin oxide Metal oxides such as metal oxides, yttrium oxide, lanthanum oxide, zirconium oxide, aluminum oxide, magnesium oxide, silicon oxide, metal fluorides such as lithium fluoride, magnesium fluoride, aluminum fluoride, cryolite, and metals such as calcium phosphate Phosphate, calcium carbonate and other carbonates, barium sulfate, magnesium sulfate and other sulfates, silicon nitride, boron nitride, carbon nitride and other nitrides, wollastonite, sepiolite, xonotlite, etc. Carbonate compounds such as titanate of silicate, potassium titanate, strontium titanate, other carbon, fullerene, carbon fiber, carbon nanotube, silicon carbide, etc. Moreover, two or more types of these particles can also be used.

In the polyester film of the present invention, in view of the large number of users who need electrical insulation, the material of the plate-like particles (b1) and needle-like particles (b2) is preferably zinc oxide, which does not have conductivity. Metal oxides such as titanium oxide, cesium oxide, antimony oxide, tin oxide, indium tin oxide, yttrium oxide, lanthanum oxide, zirconium oxide, aluminum oxide, magnesium oxide, silicon oxide, etc. Metal fluorides such as lithium fluoride, magnesium fluoride, aluminum fluoride, cryolite, metal phosphates such as calcium phosphate, carbonates such as calcium carbonate, sulfates such as barium sulfate, magnesium sulfate, silicon nitride, nitride Boron, carbon nitride and other nitrides, wollastonite, sepiolite, xonotlite and other silicates, potassium titanate and other titanates, etc. In such cases, the insulating properties of the particles are utilized, and the electrical insulating properties are maintained for a long period of time, and the effects of the present invention are remarkably exhibited.

The polyester film of the present invention contains at least one kind of plate-like particles (b1) with an aspect ratio of 2 or more and needle-like particles (b2) with an aspect ratio of 2 or more in the crystalline polyester (A), and has a layer ( In the film of P layer), the sum of the contents of the plate-like particles (b1) having an aspect ratio of 2 or more and the acicular particles (b2) having an aspect ratio of 2 or more contained in the P layer is 10% by mass or more.

As long as it contains at least any one of plate-like particles (b1) with an aspect ratio of 2 or more and needle-like particles (b2) with an aspect ratio of 2 or more in the P layer, it is more preferable to contain plate-like particles (b1) and needles Both particles (b2). At this time, when the content of the plate-like particles (b1) with an aspect ratio of 2 or more is regarded as Wb1 (mass %), and the content of the acicular particles (b2) with an aspect ratio of 2 or more is regarded as Wb2 (mass%), Wb2/ Wb1 of 0.7 or more and 9 or less is preferable because of improved thermal conductivity. More preferably, it is 1 or more and 8 or less, and particularly preferably 2 or more and 7 or less. If Wb2/Wb1 is too small or too large, the contact probability between the plate-shaped particles and the needle-shaped particles decreases, and the degree of increase in the thermal conductivity in the thickness direction of the thin film may become small.

The polyester film of the present invention must have a Young's modulus of 2 GPa or more. In addition, the Young's modulus mentioned here is the Young's modulus of the film measured by changing the direction every 10° in the film surface. The Young's modulus in the direction where the Young's modulus becomes the largest and the direction Young's in orthogonal direction The average value of the modulus Eb. The Young's modulus is more preferably 2 GPa or more, and particularly preferably 3 GPa or more. The Young's modulus system is related to the alignment/crystalline state of the crystalline polyester (A). A polyester film with a Young's modulus of less than 2 GPa indicates that the crystalline polyester (A) has reduced alignment/crystallinity and heat resistance. Or the dimensional stability is reduced. In the polyester film of the present invention, by setting the Young's modulus to 2 GPa or more, good heat resistance and dimensional stability can be obtained.

The polyester film of the present invention is obtained by dynamic viscoelasticity measurement at a frequency of 1 Hz (hereinafter, described as DMA). The dynamic storage elastic modulus E′ at 100° C. is preferably 5×10 ⁷ Pa or more, more preferably 1 ×10 ⁸ Pa or more, particularly preferably 5×10 ⁸ Pa or more. A polyester film with a small E'means that the crystalline polyester (A) has reduced alignment/crystallinity, and may have reduced heat resistance or dimensional stability. In the polyester film of the present invention, by setting E′ to 5×10 ⁷ Pa or more, good heat resistance and dimensional stability can be obtained.

In the polyester film of the present invention, when the content of the particles (B) in the P layer is regarded as Wb (mass %), and the porosity in the P layer is regarded as V (volume %), V/Wb must be 1 the following. The porosity mentioned here is the ratio of the area of the void occupied in the cross-sectional area of the film in the cross-sectional SEM image of the P layer, and this ratio is taken as the porosity V (volume %). It is more preferably 0.8 or less, particularly preferably 0.6 or less, and particularly preferably 0.5 or less. If V/Wb exceeds 1, the film has a large amount of air with low thermal conductivity, and as a result, the thermal conductivity of the film decreases. The lower limit of V/Wb is 0. In the polyester film of the present invention, by setting V/Wb to 1 or less, high thermal conductivity can be obtained.

唑啉基、環氧基、碳二亞胺基、異氰酸酯基、酸酐基等之取代基。特別當從與聚酯的反應性高，且所形成的鍵結之耐熱性高之觀點來看，特佳為環氧基。特別是藉由在粒子(B)之表面上具有反應性取代基(a)，則於結晶性聚酯(A)與粒子(B)之混練時形成鍵結，藉此而形成強固的界面，故於後述的延伸步驟中，在結晶聚酯(A)與粒子(B)之界面，可抑制界面剝離。 In order to obtain a polyester film with a Young's modulus of 2 GPa or more, the polyester composition containing the P layer must be stretched at least in the uniaxial direction, but usually in the stretching step, the crystalline polyester (A) and The interface between the particles (B) is peeled off to form pores, and V/Wb will exceed 1. In the polyester film of the present invention, in order to make the Young's modulus 2 GPa or more and V/Wb 1 or less, it is preferably used on the surface of the aforementioned particles (B) to have reactivity with the crystalline polyester (A) Of substituents (hereinafter described as reactive substituents (a)). The reactive substituent (a) mentioned here is a substituent capable of reacting and bonding with a carboxyl terminal group or a hydroxyl terminal group of a polyester, and specifically includes

Substituents such as oxazoline, epoxy, carbodiimide, isocyanate, and anhydride groups. In particular, from the viewpoint of high reactivity with polyester and high heat resistance of the formed bond, it is particularly preferably an epoxy group. Especially by having a reactive substituent (a) on the surface of the particle (B), a bond is formed when the crystalline polyester (A) and the particle (B) are kneaded, thereby forming a strong interface, Therefore, in the extension step described later, the interface peeling can be suppressed at the interface between the crystalline polyester (A) and the particles (B).

In the polyester film of the present invention, the amount of the reactive substituent (a) per unit surface area of the particles (B) is preferably 0.2×10 ⁻⁶ mol/m ² or more and 1.4×10 ⁻⁴ mol/m ² or less It is more preferably 1×10 ^-5 mol/m ² or more and 1×10 ^-4 mol/m ² or less, and particularly preferably 1.3×10 ^-5 mol/m ² or more and 5×10 ^-5 mol/m ² or less. If it is less than 0.2×10 ^-6 , the bonding between the crystalline polyester (A) and the particles (B) becomes insufficient, and interfacial peeling occurs significantly during elongation, resulting in a decrease in thermal conductivity. In addition, if it exceeds 1.4×10 ^-4 mol/m ² , the amount of bonding becomes excessive and the extensibility decreases. In the polyester film of the present invention, since the amount of the reactive substituent (a) per unit surface area of the particles (B) becomes 0.2×10 ⁻⁶ mol/m ² or more and 1.4×10 ⁻⁴ mol/m ² or less, Therefore, thermal conductivity and extensibility can coexist.

The amount of the reactive substituent (a) of the particles (B) can be obtained by a known titration method. For example, taking the case of an epoxy group as an example, in the present invention, it is obtained by the following method. After dispersing the particles (B) in water to make a prepared solution, HCl-CaCl ₂ reagent is added, after the reaction is performed at a certain temperature and a certain time, a known amount of KOH is added excessively to stop the reaction, and phenolphthalein is used as an indicator , Reverse titration with HCl aqueous solution. The titration is performed on the surface-treated particles (B) and the non-surface-treated particles (B). The latter titration result is used as a blank group, the consumed HCl is obtained, and the amount of epoxy groups in the sample solution is calculated ( mol). In addition, the surface area (m ² ) of the particles (B) is determined by the BET method described in JIS Z 8830 (2013), and the amount of epoxy groups (mol) obtained by the above method is divided by the BET method Surface area (m ² ), the amount of reactive substituent (a) (mol/m ² ) is determined.

唑啉基、環氧基、碳二亞胺基、酸酐基、異氰酸酯基的矽烷偶合劑、鈦偶合劑、鋁酸鹽系偶合劑，其中宜使用2-(3,4-環氧基環己基)乙基三甲氧基矽烷、3-環氧丙氧基丙基甲基二甲氧基矽烷、3-環氧丙氧基丙基三甲氧基矽烷、3-環氧丙氧基丙基甲基二乙氧基矽烷、3-環氧丙氧基丙基三乙氧基矽烷、環氧丙氧基辛基三甲氧基矽烷等之具有環氧基的矽烷偶合劑、3-異氰酸酯基丙基三乙氧基矽烷、3-異氰酸酯基丙基三甲氧基矽烷等之具有異氰酸酯基的矽烷偶合劑、3-三甲氧基矽烷基丙基琥珀酸酐等之具有酸酐基的矽烷偶合劑等。又，亦宜使用具有反應性取代基(a)的烷氧基寡聚物等。另外，亦宜使用甲基丙烯酸環氧丙酯等之具有環氧基的單體，或甲基丙烯酸2-異氰酸酯基乙酯等之具有 異氰酸酯基的單體與苯乙烯或乙烯、丙烯、丙烯酸等共聚合之樹脂，聚碳二亞胺、含有

唑啉基的樹脂等。於此等之中，基於結晶性聚酯(A)與粒子(B)之兩者能形成鍵結且形成強固的界面之觀點，特佳為2-(3,4-環氧基環己基)乙基三甲氧基矽烷、3-環氧丙氧基丙基甲基二甲氧基矽烷、3-環氧丙氧基丙基三甲氧基矽烷、3-環氧丙氧基丙基甲基二乙氧基矽烷、3-環氧丙氧基丙基三乙氧基矽烷、環氧丙氧基辛基三甲氧基矽烷等之具有環氧基的矽烷偶合劑、3-異氰酸酯基丙基三乙氧基矽烷、3-異氰酸酯基丙基三甲氧基矽烷等之具有異氰酸酯基的矽烷偶合劑、3-三甲氧基矽烷基丙基琥珀酸酐等之具有酸酐基的矽烷偶合劑、具有反應性取代基(a)的烷氧基寡聚物。還有，亦較宜使用上述具有反應性取代基(a)的表面處理劑彼此之混合、具有反應性取代基(a)的表面處理劑與不具有反應性取代基的表面處理劑之混合。 In the polyester film of the present invention, the particles (B) are preferably treated with a surface treatment agent having a reactive substituent (a). As a specific example of the surface treatment agent, there may be mentioned

The oxazoline group, epoxy group, carbodiimide group, acid anhydride group, isocyanate group silane coupling agent, titanium coupling agent, aluminate type coupling agent, among which 2-(3,4-epoxycyclohexyl group is preferred ) Ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyl Epoxy-containing silane coupling agent such as diethoxysilane, 3-glycidoxypropyltriethoxysilane, glycidoxyoctyltrimethoxysilane, 3-isocyanatopropyltris Silane coupling agent with isocyanate group such as ethoxysilane, 3-isocyanatopropyltrimethoxysilane, etc. Silane coupling agent with acid anhydride group such as 3-trimethoxysilylpropyl succinic anhydride, etc. In addition, it is also preferable to use an alkoxy oligomer having a reactive substituent (a). In addition, monomers having epoxy groups such as glycidyl methacrylate, or monomers having isocyanate groups such as 2-isocyanatoethyl methacrylate and styrene or ethylene, propylene, acrylic acid, etc. are also preferably used Copolymerized resin, polycarbodiimide, containing

Oxazoline-based resins. Among these, from the viewpoint that both the crystalline polyester (A) and the particles (B) can form a bond and form a strong interface, 2-(3,4-epoxycyclohexyl) is particularly preferred Ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldi Ethoxy silane, 3-glycidoxypropyl triethoxy silane, glycidoxy octyl trimethoxy silane and other epoxy-containing silane coupling agent, 3-isocyanatopropyl triethyl Silane coupling agent with isocyanate group such as oxysilane, 3-isocyanatopropyltrimethoxysilane, etc. Silane coupling agent with acid anhydride group such as 3-trimethoxysilylpropyl succinic anhydride, and reactive substituent (a) The alkoxy oligomer. In addition, it is also preferable to use a mixture of the above-mentioned surface treatment agents having a reactive substituent (a), and a mixture of a surface treatment agent having a reactive substituent (a) and a surface treatment agent having no reactive substituent.

In the polyester film of the present invention, the P layer will contain at least one of the crystalline polyester (A) and plate-like particles (b1) with an aspect ratio of 2 or more and needle-like particles (b2) with an aspect ratio of 2 or more The resin composition is obtained by the manufacturing method described later, but the difference ΔTcg between the glass transition temperature Tg of the P layer and the cold crystallization peak top temperature Tcc is preferably 44° C. or higher. The glass transition temperature Tg and the cold crystallization peak-top temperature Tcc mentioned here are the glass transition temperature Tg and the cold crystallization peak-top temperature Tcc in the heating process (heating rate: 20°C/min), according to JIS K- The method of 7121 (1987), the differential scanning calorimetry of 2ndRUN obtained by the method described later, the glass transition temperature Tg and the cold crystallization peak top temperature Tcc in the figure, and the obtained Tg value and The difference in Tcc value is regarded as ΔTcg. △Tcg is more preferably 45°C or more and 50°C or less. If ΔTcg is low, stretching becomes difficult, and the film formability may decrease. In the polyester film of the present invention, since ΔTcg is 44° C. or higher, good film formability can be obtained. In order to make ΔTcg 44°C or higher, a method of increasing the IV of the crystalline polyester (A) in the P layer can be cited as a preferable method. As a means to increase the IV of the crystalline polyester (A), in the production method described later, it is particularly preferable to obtain a fragmented composition after mixing the crystalline polyester (A) and particles (B), and then obtain the After solid phase polymerization of the fragments, a film is made.

The polyester film of the present invention may be a single-layer film composed only of the above-mentioned P layer, or a laminated film composed of laminated layers with other layers (hereinafter, other layers will be simply referred to as P2 layers), and may be used. . In the case of a laminated structure, in order to exert the effect of high heat resistance of the P layer, the ratio of the P layer is preferably 40% by volume or more of the entire polyester film, more preferably 50% by volume or more, and particularly preferably 70% by volume or more , Tejia is more than 80% by volume. If the proportion of the P layer is less than 40% by volume, the effect of improving the heat resistance caused by the P layer will not be exhibited. In the polyester film of the present invention, in the case of a laminated structure, since the ratio of the P layer is 40% by volume or more, higher heat resistance than the conventional polyester film can be obtained.

In the polyester film of the present invention, the thickness of the P layer is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 400 μm or less, and particularly preferably 20 μm or more and 300 μm or less. When the thickness is less than 5 μm, the film formability of the thin film becomes low, and film forming may become difficult. On the other hand, when it is thicker than 500 μm, for example, when the electrical insulating sheet using the thin film is processed, cutting or folding becomes difficult. In the polyester film of the present invention, by making the thickness of the P layer 5 μm or more and 500 μm or less, the film-forming property and the processability can coexist.

The thickness of the entire polyester film of the present invention is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 400 μm or less, and particularly preferably 20 μm or more and 300 μm or less. When the thickness is less than 5 μm, the film formability of the thin film becomes low, and film forming may become difficult. On the other hand, when it is thicker than 500 μm, for example, when the electrical insulating sheet using the thin film is processed, cutting or folding becomes difficult. In the polyester film of the present invention, by making the thickness of the entire film 5 μm or more and 500 μm or less, the film-forming property and the processability can coexist.

The elongation at break of the polyester film of the present invention is preferably 10% or more, more preferably 20% or more, and particularly preferably 30% or more. In the polyester film of the present invention, if the elongation at break is less than 10%, the film may be easily broken during processing such as transportation or cutting during film formation or continuous processing. In the polyester film of the present invention, by making the elongation at break 10% or more, the film forming property and the processability can coexist. As a means to achieve this, it can be mentioned that in the production method described later, the treatment amount of the surface treatment agent is included in a more preferable range, especially when the crystalline polyester (A) and the particles (B) are mixed to obtain a chip form After the composition of the composition, after solid-phase polymerization of the resulting fragments, the process of making a film.

The thermal conductivity of the polyester film of the present invention in the thickness direction of the film is preferably 0.15 W/mK or more, more preferably 0.20 W/mK or more, and particularly preferably 0.25 W/mK or more. By satisfying this value, it can be applied to motor insulation materials (such as wind power generation insulation sheets, hybrid motor sheets, air conditioner motor sheets), solar cell backplanes, and electrical insulating materials used in electronic parts (for example, electronic Adhesive tape for parts, flexible printed circuit board, membrane switch, etc.) etc. As a means to increase the thermal conductivity in the thickness direction of the film, In addition to the above-mentioned preferred raw material formulation, in particular, after mixing the crystalline polyester (A) and the particles (B) to obtain a fragmented composition, the resulting fragments are solid-phase polymerized to produce a film , As the preferred method.

The polyester film of the present invention preferably has a surface specific resistance of 10 ¹³ Ω/□ or more. By satisfying this value, it can be applied to motor insulating materials (such as insulating sheets for wind power generation, sheets for hybrid motors, sheets for air-conditioning motors), electrical insulating materials for solar cell backplanes, electronic parts (for example, electronic Adhesive tape for parts, flexible printed circuit board, membrane switch, etc.) etc.

In the polyester film of the present invention, as an example of a P2 layer laminated on a polyester layer (P layer), a polyester layer for function imparting, an antistatic layer, an adhesion layer with other materials, and ultraviolet resistance can be formed UV-resistant layer for imparting properties, flame-retardant layer for imparting flame retardancy, hard coating layer for improving impact resistance and scratch resistance, etc., any layer depending on the intended use.

The polyester film of the present invention is evaluated according to the UL94-VTM test method. The burning distance is preferably 125 mm or less, more preferably 115 mm or less, particularly preferably 105 mm or less, especially 100 mm or less, and particularly preferably 95 mm or less. In the polyester film of the present invention, when the burning distance when evaluated according to the UL94-VTM test method is 125 mm or less, for example, when it is used as a back sheet for solar cells, it can become more safe.

Next, an example of the method for manufacturing the polyester film of the present invention will be described, but the present invention is not limited to such an example.

The manufacturing method of the polyester film of the present invention includes the following steps 1 to 3 in sequence.

(Step 1) The crystalline polyester (A) and aspect ratio 2 or more The step of melting and kneading at least one of the plate-like particles (b1) and the needle-like particles (b2) having an aspect ratio of 2 or more. In particular, a crystalline polyester (A) and a board having a substituent that is reactive with the crystalline polyester (A) on the surface (hereinafter, described as a reactive substituent (a)) and having an aspect ratio of 2 or more Step of melt-kneading at least one kind of particles (b1), needle-like particles (b2) having a reactive substituent (a) on the surface and an aspect ratio of 2 or more (hereinafter, described as a melt-kneading step), (step 2) A resin composition containing at least one of crystalline polyester (A) and plate-like particles (b1) having an aspect ratio of 2 or more and needle-like particles (b2) having an aspect ratio of 2 or more is melted and discharged from a nozzle to obtain The step of the film (hereinafter referred to as the melt extrusion step), (step 3) the step of biaxially stretching the film (hereinafter referred to as the stretching step)

Hereinafter, Step 1 to Step 3, etc. will be described in detail.

(step 1)

In the method for producing a polyester film of the present invention, the crystalline polyester (A) used as the raw material is obtained through the esterification reaction or the transesterification reaction from the above-mentioned dicarboxylic acid component and diol component. The polycondensation reaction is carried out so that the inherent viscosity becomes 0.4 or more.

In addition, when performing a transesterification reaction, in addition to known transesterification catalysts such as magnesium acetate, calcium acetate, manganese acetate, and cobalt acetate, antimony trioxide, which is a polymerization catalyst, may be added. When an alkali metal such as potassium hydroxide of a few ppm is added during the esterification reaction, by-products of diethylene glycol can be suppressed, and heat resistance or hydrolysis resistance can also be improved.

In addition, as a polycondensation reaction catalyst, an ethylene glycol solution of germanium dioxide, antimony trioxide, titanium alkoxide, titanium chelate compound, or the like can be used.

As other additives, for example, for the purpose of imparting static electricity application characteristics, magnesium acetate, calcium acetate as an auxiliary catalyst, etc. may be mentioned, and they may be added within a range that does not hinder the effect of the present invention. In addition, in order to impart smoothness to the film, various particles may be added, or particles containing precipitates inside the catalyst may be added.

In the method for producing a polyester film of the present invention, when the particles (B) have a reactive substituent (a), the particles (B) include (i) after dispersing the particles in a solvent, the dispersion liquid is stirred Method of adding surface treatment agent or solution/dispersion solution of dissolved/dispersed surface treatment agent, (ii) Method of adding solution/dispersion solution of dissolved/dispersed surface treatment agent while stirring powder of particles . In addition, when the surface treatment agent is a resin system, it is also preferable to use (iii) a method of melting and kneading the particles and the surface treatment agent. When the addition amount of the surface treatment material agent is 100 parts by mass of the content Wb of the particles (B), the mass ratio of the surface treatment agent is preferably 0.1 parts by mass or more and 5 parts by mass or less, more preferably 0.2 parts by mass or more 3 Below mass parts, particularly preferably 0.5 mass parts or more and 1.5 mass parts or less. If it is less than 0.1 parts by mass, the bond between the crystalline polyester (A) and the particles (B) becomes insufficient, and interfacial peeling significantly occurs during elongation, resulting in a decrease in thermal conductivity. In addition, if it exceeds 5 parts by mass, the amount of bonding becomes excessive and the extensibility decreases.

Next, the method of adding plate-like particles (b1) or needle-like particles (b2) to the crystalline polyester (A) obtained through the above is preferably using an exhaust type biaxial kneading extruder or tandem extrusion Press, the crystalline polyester (A) A method of melt-kneading with plate-like particles (b1), or crystalline polyester (A) and needle-like particles (b2). At this time, in order not to destroy the shape of the plate-like particles (b1) or needle-like particles (b2) during melt-kneading, it is preferable to supply the plate-like particles (b1) in a state where the crystalline polyester (A) is molten. Or needle-shaped particles (b2) are supplied to the extruder by lateral feed.

Here, when melt-kneading containing platy particles (b1) or needle-like particles (b2) in the crystalline polyester (A), many crystalline polyesters (A) are deteriorated due to heat history. Therefore, a high-concentration master pellet (master pellet) with an added amount larger than the content of plate-like particles (b1) or needle-like particles (b2) in the P layer is prepared, mixed with and diluted with the crystalline polyester (A) , The amount of plate-like particles (b1) or needle-like particles (b2) in the P layer is a predetermined content, the deterioration of the crystalline polyester (A) can be suppressed, from the extensibility, mechanical properties, heat resistance, etc. From a viewpoint, it is better.

At this time, the concentration of particles in the high-concentration masterbatch particles is preferably 20% by mass or more and 80% by mass or less, more preferably 25% by mass or more and 70% by mass or less, and particularly preferably 30% by mass or more and 60% by mass or less. It is preferably 40% by mass or more and 60% by mass or less. When it is less than 20% by mass, the amount of masterbatch particles added to the P layer increases, and as a result, the amount of the crystalline polyester (A) that has deteriorated in the P layer increases, and the elongation, mechanical properties, and heat resistance may decrease. In addition, when it exceeds 80% by mass, granulation of the masterbatch becomes difficult, or when the masterbatch particles are mixed in the crystalline polyester (A), it may become difficult to uniformly mix.

In addition, a method of containing both the plate-like particles (b1) and the needle-like particles (b2) in the crystalline polyester (A) includes the mother of the crystalline polyester (A) containing the plate-like particles (b1) Material particles, and crystallinity containing needle-like particles (b2) Masterbatch particles of polyester (A) are prepared separately, and they are mixed with crystalline polyester (A) and diluted to contain plate-like particles (b1) and needle-like particles (P1) of the P layer at a predetermined ratio ( b2) The method of adjusting the amount of method, or when preparing the masterbatch particles, adjust the ratio of the plate-like particles (b1) to the needle-like particles (b2) to the specified ratio to produce the masterbatch particles, and then Any method such as a method of mixing and diluting with crystalline polyester (A) may be used.

Using the composition obtained through the above step 1, the following description will be made (step 2) to produce high-concentration masterbatch particles with a content greater than that of the plate-like particles (b1) or needle-like particles (b2) contained in the P layer, and use The solid phase polymerization of the obtained masterbatch particles is particularly preferable in terms of increasing the molecular weight and further reducing the number of carboxyl terminal groups. In the solid-phase polymerization, the solid-phase polymerization temperature is preferably such that the melting point of the polyester is Tm-30°C or lower, the melting point Tm-60°C or higher, and the solid-phase polymerization reaction is performed at a vacuum of 0.3 Torr or lower.

(Step 2)

Next, the step of forming the composition comprising the crystalline polyester (A) and the particles (B) composed of plate-like particles (b1) and needle-like particles (b2) obtained in the above step 1 into a sheet shape will be described.

When the polyester film of the present invention is composed of a single film made of only the P layer, the raw material for the P layer can be heated and melted in the extruder, extruded from the nozzle onto the cooled casting drum, and processed into Sheet method (melt casting method). As another method, it is also possible to dissolve the raw material for the P layer in a solvent, extrude the solution from a nozzle onto a support such as a casting drum, an endless belt, etc. to form a film, and then dry it from the film layer The method of removing the solvent and processing into sheets (solution casting method), etc. among them, From the viewpoint of high productivity, it is preferably formed into a sheet shape by a melt casting method (hereinafter, the step of forming into a sheet shape by a melt casting method is referred to as a melt extrusion step).

In the method for producing a polyester film of the present invention, at the time of production in the melt extrusion step, at least one of the dried crystalline polyester (A), plate-like particles (b1) and needle-like particles (b2) A particle composition is melt extruded from a nozzle into a sheet shape using an extruder, and is cooled and solidified by static electricity on a roller whose surface temperature is cooled to above 10°C and below 60°C to produce an unstretched sheet. It can be obtained by biaxially extending this unextended sheet.

When melt extruding with an extruder, the melt is made under a nitrogen atmosphere, and the time from the supply of the fragments of the extruder to the extrusion to the nozzle is as short as possible. The target is 30 minutes or less, more preferably 15 minutes Below, particularly preferably 5 minutes or less, which is preferable from the viewpoint of the suppression of deterioration due to the decrease in molecular weight and the suppression of the increase in the number of carboxyl terminal groups

(Step 3)

The sheet-like composition obtained in step 2 is biaxially stretched at a temperature above the glass transition temperature Tg. As the method of biaxial stretching, either a stepwise biaxial stretching method may be performed to separate the extension in the longitudinal direction and the width direction, or any one of a simultaneous biaxial stretching method in which the longitudinal direction and the width direction are simultaneously extended. An example of stretching conditions may include: (1) In the case of simultaneous biaxial stretching, the stretching temperature is set to a temperature in the range of Tg above Tg+15°C or below of the glass transition temperature of the polyester, (2) Biaxial stepwise In the case of elongation, the elongation temperature of the first axis is defined as the temperature at which the glass transition temperature of the polyester is Tg or higher Tg+15°C or lower (more preferably Tg or higher Tg+10°C or lower) Degree, the extension temperature of the second axis is set to a temperature of Tg+5°C or higher and Tg+25°C or lower.

The stretch magnification is 1.5 times or more and 4 times or less in the longitudinal direction and the width direction in both simultaneous biaxial stretching and stepwise biaxial stretching, more preferably 2.0 times or more and 3.5 times or less, and particularly preferably 2.0 times or more and 3.0 times or less. The area stretching magnification combining the longitudinal stretching magnification and the lateral stretching magnification is 2 times or more and 16 times or less, preferably 4 times or more and 13 times or less, and more preferably 4 times or more and 9 times or less. If the area ratio is less than 2 times, the orientation of the crystalline polyester (A) of the resulting film will be low, and the mechanical strength or heat resistance of the resulting film will decrease. In addition, if the area stretching ratio exceeds 14 times, breakage is likely to occur during stretching, and the resulting film has a tendency to increase the porosity V or decrease the thermal conductivity.

In order to fully perform the crystal orientation of the obtained biaxially stretched film, and to impart flatness and dimensional stability, the crystalline polyester (A) has a glass transition temperature Tg or higher and a temperature Th that is lower than the melting point Tm for 1 second or more and 30 seconds. The following heat treatment is gradually cooled uniformly and then cooled to room temperature. In the manufacturing method of the polyester film of the present invention, the difference Tm-Th between the heat treatment temperature Th and the melting point Tm of the polyester is 20°C or more and 90°C or less, preferably 25°C or more and 70°C or less, more preferably 30°C or more Below 60℃. In addition, in the above heat treatment step, if necessary, a relaxation treatment of 3 to 12% may be performed in the width direction or the longitudinal direction. Then, as necessary, in order to further improve the adhesion with other materials, corona discharge treatment or the like is performed, and coiling is performed, whereby a P layer can be obtained.

In addition, the manufacturing method of the polyester film of the present invention having a layered structure including a P layer and other layers (P2 layer) is as follows. When accumulated When the material of each layer is made of thermoplastic resin, two different materials can be put into two extruders respectively to be melted and co-extruded from the nozzle to the cooled casting drum and processed into Sheet-like method (co-extrusion method); on at least one side of a sheet made of a single layer, the raw material of the coating layer is put into an extruder for melt extrusion, and the method of laminating while extruding from a nozzle (melt lamination) Method); separately prepare the P layer and the stacked P2 layer, a method of heat pressing by a heated roller group, etc. (heat lamination method); a method of bonding via an adhesive (adhesion method); A method for dissolving the material for the P2 layer in a solvent and applying the solution to the P layer prepared in advance (coating method); and a method combining these methods.

In addition, when the P2 layer is made of a material that is not a thermoplastic resin as the main component, the P layer and the stacked P2 layer can be separately prepared and bonded by an adhesive or the like (adhesion method), or as hardenability In the case of materials, it can be applied to the method of hardening by electromagnetic wave irradiation, heat treatment, etc. after coating on the P layer. In addition to the above-mentioned methods such as co-extrusion, fusion lamination, solution lamination, and thermal lamination, dry methods such as vapor deposition, sputtering, and wet methods such as plating can also be suitably used. Wait.

As a method of forming a layer P2 made of different materials by a coating method, an in-line coating method applied to the film formation of the polyester film of the present invention, a polyester applied to the film formation Either off-line coating method on the film can be used, but for the reason that it can be coated at the same time as the polyester film and is efficient, and the adhesion to the polyester film is high, it is better to use wire Internal coating method. In addition, corona treatment on the surface of the polyester film is also suitable for coating.

The polyester film of the present invention can be formed by the above steps, and the resulting film has high thermal conductivity and mechanical properties. The polyester film of the present invention utilizes its advantages, and can be suitably used in, for example, copper-clad laminates, solar cell back sheets, adhesive tapes, flexible printed circuit boards, membrane switches, planar heating elements, flat cables, etc. Electrical insulation materials, capacitor materials, automotive materials, and building materials represent applications that value electrical insulation and thermal conductivity. Among them, it is better to use electrical insulating materials for motors (such as insulating sheets for wind power generation, hybrid motor sheets, air-conditioning motor sheets), solar cell back sheet materials, and electrical components Insulating materials (for example, adhesive tape for electronic parts, flexible printed circuit boards, membrane switches, etc.). The polyester film of the present invention is superior to the conventional polyester film due to its thermal conductivity and mechanical properties, for example, when an electrical insulating sheet (insulating sheet for wind power generation, etc.) or solar cell back sheet made of the polyester film of the present invention is used Compared with conventional wind power generators and solar cells, it can improve power generation efficiency. In addition, when used in hybrid motor blades and air conditioner motor blades, power consumption can be reduced. In addition, when the polyester film of the present invention is used in an adhesive tape for electronic parts, a flexible printed circuit board, a membrane switch, etc., not only can the power consumption be reduced, but also the speed of operation or the reliability can be improved.

[Characteristic evaluation method]

A. Analysis of the composition of polyester

The polyester is hydrolyzed by an alkali, and each component is analyzed by a gas chromatograph or a high-speed liquid chromatograph, and the composition ratio is obtained from the peak area of each component. An example is shown below. The dicarboxylic acid constituents or other constituents were measured with a high-speed liquid chromatograph. Measurement conditions can be divided by known methods The analysis shows an example of the measurement conditions below.

Device: Shimadzu LC-10A

Column: YMC-Pack ODS-A 150×4.6mm S-5μm 120A

Column temperature: 40℃

Flow rate: 1.2ml/min

Detector: UV 240nm

The quantification of diol constituents or other constituents can be analyzed by a known method using a gas chromatograph. An example of measurement conditions is shown below.

Installation: Shimadzu 9A (Shimadzu Corporation (share) system)

Column: SUPELCOWAX-10 capillary column 30m

Column temperature: 140℃~250℃ (heating rate 5℃/min)

Flow rate: nitrogen 25ml/min

Detector: FID.

B. Intrinsic viscosity IV

In 100ml of o-chlorophenol, dissolve the polyester film (layer P is the case of P layer) (polyester concentration in the solution C = 1.2g/ml), use Ostwald (Ostwald) viscometer to determine the solution at 25 °C viscosity. In addition, the viscosity of the solvent was measured in the same manner. Using the obtained solution viscosity and solvent viscosity, [η] is calculated by the following formula (1), and the obtained value is regarded as the intrinsic viscosity (IV).

ηsp/C=[η]+K[η] ² ‧C (1)

(Here, ηsp=(solution viscosity/solvent viscosity)-1, K is Huggins constant (0.343)). In addition, the measurement is performed after separating the particles (B).

C. Glass transition temperature Tg, cold crystallization temperature Tcc of P layer 、The melting point Tm of crystalline polyester (A), the heat of crystallization melting △Hm

According to JIS K-7121 (1987) and JIS K-7122 (1987), the measuring device is a differential scanning calorimeter measuring device "Robot DSC-RDC220" manufactured by SEIKO Electronics Industries Co., Ltd., and the data analysis is using Disksession "SSC/5200" ", using the following method to measure the polyester film (in the case of laminated film is the P layer cut out).

(1) 1stRUN measurement

Weigh 5mg of each polyester film on the sample pan (in the case of a laminated film, the P layer is cut out), and heat the resin from 25°C to 300°C at a heating rate of 20°C/min. Hold for 5 minutes in the state, and then quench to 25°C or lower.

(2) 2ndRUN

Immediately after the completion of the 1stRUN measurement, the temperature was raised from room temperature to 300°C at a temperature increase rate of 20°C/min, and the measurement was performed.

In the obtained differential scanning calorimetry chart of 2ndRUN, the glass transition temperature is in the step change of glass transition, according to JIS K-7121 (1987) "9.3 How to Find the Glass Transition Temperature (1) Mid-point glass transition The method described in "Temperature Tmg" is used to obtain the glass transition temperature Tg of the crystalline polyester (A) (a straight line at a middle distance in the longitudinal direction from the straight line extending each base line intersects the curve of the step-like change part of the glass transition Click to get). In addition, the peak top temperature in the cold crystallization peak is used as the cold crystallization peak temperature Tcc of the crystalline polyester (A) of the P layer. Using the obtained values of Tg and Tm, the difference ΔTcg between the glass transition temperature Tg of the P layer and the cold crystallization peak top temperature Tcc is determined by the following formula (2).

△Tcg=Tcc-Tg (2)

In addition, the thermal properties (melting point Tm, crystal melting heat △Hm) of the crystalline polyester (A) used as the raw material were measured using the crystalline polyester (A) in the same manner as the above method. In the differential scanning calorimetry chart, the peak top temperature of the crystal melting peak is taken as the melting point Tm. In addition, the heat of crystal melting ΔHm is based on JIS K-7122 (1987) "9. Method for determining the heat of transfer" to obtain the heat of crystal melting peak.

D. Young's modulus, elongation at break

The elongation at break of the polyester film is based on ASTM-D882 (1997), a size of 1 cm x 20 cm is cut out from the sample, and the elongation at break when stretched at 5 cm between the jigs and at a stretching speed of 300 mm/min is measured. Furthermore, the Young's modulus was obtained from the obtained load-strain curve. In addition, the measurement system was performed 5 times for each sample, and the average value was used.

When determining the direction in which the Young's modulus becomes the largest (direction a), consider any direction as 0°, change the direction every 10° from -90° to 90° in the film surface, and measure the same to determine Young's The direction in which the modulus becomes maximum (direction a), the Young's modulus Ea is obtained. Then, the Young's modulus Eb in the direction (direction b) orthogonal to the same plane as the direction a is obtained. The average value of the obtained Ea and Eb was taken as the Young's modulus. In addition, the fracture elongation is the average value of the fracture elongation in the direction a and the direction b as the fracture elongation.

E. Porosity V

The porosity is obtained by the following procedures (A1) to (A5). In addition, the measurement system arbitrarily changed the film cutting position and performed 10 times, and the average value of the addition was used as the porosity V (vol%) in the P layer.

(A1) Using a micro-slicer, the film cross section is cut perpendicular to the film surface direction without crushing the film cross section in the thickness direction.

(A2) Next, using a scanning electron microscope, the cut section was observed to obtain an image magnified at 3000 times. Furthermore, the observation place is arbitrarily determined in the P layer, but the up-down direction of the image is parallel to the thickness direction of the film, and the left-right direction of the image is parallel to the direction of the film surface.

(A3) Measure the area of the P layer in the image obtained in (A2) above, and consider it as A.

(A4) Measure the area of all voids present in the P layer in the image, and take the total area as B. Here, the measurement target is not limited to those in which the entire void is included in the video, but also includes bubbles that appear only in a part of the video.

(A5) By dividing B by A (B/A) and multiplying it by 100, the area ratio of voids in the P layer is obtained, and this value is used as the void ratio V (vol%).

F. The content Wb1 of the plate-like particles (b1) and the content Wb2 of the needle-like particles (b2) in the P layer

The content Wb1 of the plate-like particles (b1) and the content Wb2 of the needle-like particles (b2) in the P layer are the following (B1) to (B1) to ( B13).

(B1) The mass w1 of the polyester film (in the case of a laminated film, which is the P layer cut out) is measured.

(B2) A polyester film (in the case of a laminated film, the P layer that is cut out) is dissolved in hexafluoro-2-isopropanol, and the particles that are insoluble components are separated by centrifugal separation.

(B3) The particles obtained were washed with hexafluoro-2-isopropanol and centrifuged. In addition, the washing operation system is repeated until ethanol is added to the washing liquid after centrifugal separation and does not become cloudy.

(B4) After heating and distilling off the cleaning liquid of (B3), let it dry for 24 hours After that, it was vacuum dried at 60°C for 5 hours to obtain particles. The mass w2 of the obtained particles was obtained, and the total content Wb (mass %) of the particles was obtained from the following formula (3).

Wb=(w2/w1)×100 (3)

(B5) The particles obtained by (B4) were fixed on the observation stand equipped with a 3D instrument for measuring the size of the observation object, and a scanning electron microscope was used to obtain an image magnified by 3000 times.

(B6) Next, by analysing a randomly selected primary particle in the image using 3D measurement software, the external cuboid is drawn.

(B7) The longest side of the circumscribed cuboid is defined as the particle length (l), the shortest side is defined as the particle thickness (t), and the remaining side is defined as the particle width (b), and the particle size is measured. The shape of the particle is defined in one sense by the combination of these three values (l, t, b).

(B8) For (B6)~(B7), change the selected primary particles at random, and count them 500 times. For the three values of measured length (l), thickness (t), and width (b), respectively The horizontal axis is regarded as the value (μm), and the vertical axis is regarded as the number (number), and a distribution curve is drawn.

(B9) Extract the values of the peak positions of the three distribution curves drawn, and use the values as the average length (lp), average thickness (tp), and average width (bp) of the particles. Furthermore, when two or more peaks are seen in the distribution curve, it means that particles of a plurality of different shapes are mixed. At this time, all the particle shapes (a combination of lp, tp, and bp) considered from the obtained peak value are listed. Each of the 500 primary particles of the measured size is individually judged whether it is the most similar to any particle shape, and the shape type is investigated. There are counts. The result of the investigation is to consider that there are more than five shapes that are seen as containing the Shaped particles.

(B10) Regarding the number of particles that have been investigated in the shape category in (B9), the particles with a ratio of length (l) to width (b) l/b of 1 or more and 2 or less are defined as plate-like particles, and l/ Particles with b greater than 2 are defined as needle-shaped particles.

(B11) Among the 500 particles whose size has been measured in (B8), for particles defined as plate-like particles in (B10), calculate the respective virtual volumes (μm ³ ) using the formula l×t×b, and obtain Its sum Vv1 (μm ³ ). In addition, using SEM/EDX (scanning electron microscope/energy dispersive X-ray spectroscopy), particle composition analysis was performed to discriminate the chemical composition of plate-like particles, based on the chemical composition, from known literature (eg, Packing Handbook (Edited by the Japan Rubber Association, 1987) etc. The general density D1 (g/μm ³ ) of the particles is quoted, and the mass Wv1 of the plate-like particles is obtained by the formula D1×Vv1.

(B12) In the same way as (B11), among the 500 particles whose size has been measured in (B8), for the particles defined as needle-shaped particles in (B10), the apparent mass Wv2(g ).

(B13) From the following formulas (4) and (5), calculate the content Wb1 (mass %) of the plate-like particles (b1) in the P layer and the content Wb2 (mass) of the needle-like particles (b2) in the P layer %).

Wb1=Wb×(Wv1/(Wv1+Wv2)) (4)

Wb2=Wb×(Wv2/(Wv2+Wv1)) (5).

G. Thermal conductivity in the thickness direction of the film

A spray for laser light absorption (Black Guard Spray FC-153 manufactured by Fine Chemical Japan Co., Ltd.) was applied to the polyester film, and after drying, a square sample of 10 mm square was cut out, and LFA447 Nanoflash manufactured by NETZSCH using Xe flash analyzer was used. At a measurement temperature of 25°C, the thermal diffusivity α (m ² /s) in the thickness direction of the film was measured. In addition, the measurement system was performed four times, and the average value was used as the thermal diffusivity, and the thermal conductivity was obtained by the following formula (6).

Thermal conductivity (W/mK) = α (m ² /s) × specific heat (J/kg‧K) × density (kg/m ³ ) (6)

In addition, a polyester film is used for the specific heat system, and the value obtained in accordance with JIS K-7123 (1987) is used. In addition, the density is measured by using a film sample cut into a size of 30 mm × 40 mm, using an electronic hydrometer (SD-120L manufactured by MIRAGE Trading Co., Ltd.), and performing 3 times at a room temperature of 23° C. and a relative humidity of 65%. For density measurement, the average value obtained is used.

H. Heat resistance

In a direction parallel to the direction a, cut a size of 1cm×20cm from the sample, heat-treat the rectangular sample in a hot air oven at 150°C for 30 minutes, and after cooling, obtain the elongation at break according to the procedure of item D above . Using the obtained value of the elongation at break and the elongation at break in the direction a obtained from item D (elongation at break before heat treatment), the elongation retention rate was calculated by the following formula (7).

Elongation retention rate (%) = elongation at break before heat treatment / elongation at break after heat treatment × 100 (7)

Using the obtained elongation retention rate, the determination was made as follows. A is the practical range.

A: The elongation retention rate is more than 50%

D: The elongation retention rate is less than 50%.

I. Surface specific resistance

Thin film surface specific resistance digital ultra-high resistance micro-current meter R8340 (manufactured by ADVANTEST Co., Ltd.) was measured. In the measurement system, the measurement is performed at any 10 places on the two sides of the film, and the average value thereof is obtained. The lower value of the average value obtained was used as the surface specific resistance. In addition, the measurement sample system used a person who was left overnight at 23° C. and 65% Rh to perform the measurement. Use the obtained value to make a judgment as follows. A is the practical range.

A: Surface specific resistance is above 10 ¹³ Ω/□

D: The surface specific resistance is less than 10 ¹³ Ω/□.

J. Dynamic storage elastic modulus

The dynamic storage elastic modulus E'is obtained in accordance with JIS-K7244 (1999) using a dynamic viscoelasticity measuring device DMS6100 (manufactured by SEIKO Instruments Co., Ltd.). In the stretching mode, the temperature dependence of the viscoelastic properties of each film was measured under the measurement conditions of a driving frequency of 1 Hz, a distance between clamps of 20 mm, and a heating rate of 2° C./min. From this measurement result, the dynamic storage elastic modulus E'at 100°C was determined.

[Example]

Hereinafter, the present invention will be described with examples, but the present invention is not necessarily limited by these.

(raw material)

‧Crystalline polyester (A):

PET-1: using dimethyl terephthalate as the acid component and ethylene glycol as the diol component, and adding germanium oxide (polymerization catalyst) so that the germanium atoms are converted to 300 ppm relative to the polyester particles obtained. , Polycondensation reaction is carried out to obtain polyethylene terephthalate particles with an inherent viscosity of 0.64. Furthermore, this resin has a glass transition temperature Tg of 83°C and a melting point Tm It is 255℃ and the heat of crystallization melting is 37J/g.

PET-2: using dimethyl terephthalate as the acid component and ethylene glycol as the diol component, and adding germanium oxide (polymerization catalyst) so that the germanium atoms are converted to 300 ppm relative to the polyester particles obtained. , Polycondensation reaction is performed to obtain polyethylene terephthalate particles with an inherent viscosity of 0.54. The obtained polyethylene terephthalate was dried at 160°C for 6 hours, and after crystallization, solid phase polymerization was carried out at 220°C, a vacuum of 0.3 Torr, and 5 hours to obtain polyethylene terephthalate with an inherent viscosity of 0.70. ester. Furthermore, this resin has a glass transition temperature Tg of 83°C, a melting point Tm of 255°C, and a heat of crystal fusion of 35 J/g.

PET-3: Except that the solid-phase polymerization time is 8 hours, polyethylene terephthalate with an inherent viscosity of 0.80 is obtained by the same method as PET-2. Furthermore, this resin has a glass transition temperature Tg of 83°C, a melting point Tm of 255°C, and a heat of crystal fusion of 36 J/g.

‧particle

Wollastonite-1: FPW#400 (manufactured by Kinsei Matecs) is used. Acicular particles with a length of 8.0 μm and an aspect ratio of 4.

Wollastonite-2: NYAD M1250 (made by Pakistan Industrial Co., Ltd.) is used. Acicular particles with a length of 12 μm and an aspect ratio of 3.

Needle-shaped titanium oxide: FTL-100 (made by Ishihara Industries Co., Ltd.) is used. Acicular particles with a length of 1.7 μm and an aspect ratio of 13.

Boron nitride: SP3-7 (Electrochemical Industry Co., Ltd.) is used. Plate-like particles with a length of 2.0 μm and an aspect ratio of 19.

Talc: Use GH-7 (made by Linhuacheng Co., Ltd.). Plate-like particles with a length of 5.8 μm and an aspect ratio of 10.

Alumina: A4-42-2 (Showa Denko Corporation) was used. It has a length of 5 μm, an indefinite shape, and an aspect ratio of 1.

In addition, the value of the particle length (aspect ratio) contained in the polyester film (in the case of a laminated film, the P layer to be cut out) is to be treated with (C4 after the following treatments (C1) to (C3) )~(C8). In addition, the value of the particle length (aspect ratio) before being added to the resin is obtained by the procedures of (C4) to (C8).

(C1) A polyester film (in the case of a laminated film, the P layer that is cut out) is dissolved in hexafluoro-2-isopropanol, and the particles that are insoluble components are separated by centrifugal separation.

(C2) The particles obtained were washed with hexafluoro-2-isopropanol and centrifuged. In addition, the washing operation system is repeated until ethanol is added to the washing liquid after centrifugal separation and does not become cloudy.

(C3) After heating and distilling off the washing liquid of (C2), and allowing it to dry naturally for 24 hours, it was vacuum-dried at a temperature of 60°C for 5 hours to obtain particles to be observed.

(C4) On the observation stand equipped with a 3D instrument for measuring the size of the observation object, the particles are fixed, and a scanning electron microscope is used to obtain an image magnified to 3000 times.

(C5) Next, by analysing a randomly selected primary particle in the image using 3D measurement software, the external cuboid is drawn.

(C6) The longest side of the circumscribed cuboid is defined as the length of the particle (l), the shortest side is defined as the thickness of the particle (t), and the remaining side is defined as the width of the particle (b), and the size of the particle is measured. The shape of the particle is defined in one sense by the combination of these three values (l, t, b).

(C7) For (C5)~(C6), change the selected primary particles at random, and count them 500 times. For the measured three values of length (l), thickness (t), and width (b), respectively The horizontal axis is regarded as the value (μm), and the vertical axis is regarded as the number (number), and a distribution curve is drawn.

(C8) Extract the value of the peak position of the three distribution curves drawn, and use the value as the average length (lp), average thickness (tp), average width (bp) of the particle, and compare the average length with the average thickness lp/tp is regarded as the aspect ratio of the particles. Furthermore, when two or more peaks are seen in the distribution curve, it means that particles of a plurality of different shapes are mixed. At this time, all the particle shapes (a combination of lp, tp, and bp) considered from the obtained peak value are listed. Each of the 500 primary particles of the measured size is individually judged whether it is the most similar to any particle shape, and the shape type is investigated. There are counts. As a result of the investigation, the number of shapes where more than five are seen is regarded as particles containing the shape, and the aspect ratio (lp/tp) of the particles is calculated.

‧Surface treatment agent

SC-1: Epoxy-containing silane coupling agent KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.. Compound name: 3-glycidoxypropyltrimethoxysilane, molecular weight 236.3)

SC-2: Epoxy-containing silane coupling agent KBM-4803 (manufactured by Shin-Etsu Chemical Co., Ltd.). Compound name: glycidoxyoctyltrimethoxysilane, molecular weight 306.4).

(Reference example 1-1)

Wollastonite-1 was put into a Hanshall mixer and stirred. In this state, the silane coupling agent became 0.1% by mass relative to 100% by weight of the acicular particles (B2) and the silane coupling agent (ring The amount of oxygen groups was 2.8×10 ^-6 mol/m ² ), sprayed and added, heated and stirred at 70°C for 2 hours, and then taken out to obtain needle-like particles (B2) having a needle-like surface on the surface Particle (B2).

A co-rotating exhaust-type twin-screw kneading extruder (made by Japan Steel Co., Ltd., with a screw diameter of 30 mm, screw length/screw diameter) with more than one lateral feed port and one kneading paddle mixing section = 45.5) Heating to 265°C, supplying 70 parts by mass of PET-1 as crystalline polyester (A) from the independent feed port, and supplying 30 parts by mass of needle-shaped particles (B1) from the side feed port, after melt-kneading It was discharged in a strand shape, cooled with water at a temperature of 25°C, and immediately cut to produce a masterbatch particle (MB-1-1) containing 30% by weight of needle-shaped particles (B2). Table 1 shows the physical properties of the obtained masterbatch particles.

(Reference examples 1-2~1-4, 2-1~2-4, 3-1~3-4)

Except for changing the type of particles and the type and amount of surface treatment agent as described in Table 1, the same operation as in Reference Example 1-1 was carried out to produce plate-shaped particles (B1) or needle-shaped particles (B2) containing 30% by weight. ) Of masterbatch particles (MB-1-2~1-4, 2-1~2-4, 3-1~3-4). Table 1 shows the physical properties of the obtained masterbatch particles.

(Reference example 1-5)

Except not subjecting the particles to surface treatment, the same procedure as in Reference Example 1-1 was carried out to produce masterbatch particles (MB-1-5) containing 30% by weight of needle-shaped particles (B2). Table 1 shows the physical properties of the obtained masterbatch particles.

(Reference example 3-5)

Except that alumina was used as the particles, and the amount of treatment was changed as shown in Table 1, the same operation as in Reference Example 1-1 was carried out to produce 30% by weight. The masterbatch particles of the particles (MB-3-5). Table 1 shows the physical properties of the obtained masterbatch particles.

(Reference example 4-1)

The masterbatch particles (MB-1-3) obtained in Reference Example 1-3 were dried at 160°C for 6 hours and crystallized, followed by solid phase polymerization at 220°C, a vacuum of 0.3 Torr, and 6 hours to produce masterbatch particles (MB-4-1). Table 1 shows the physical properties of the obtained masterbatch particles.

(Reference example 4-2)

The masterbatch particles (MB-1-3) obtained in Reference Example 1-3 were dried at 160°C for 6 hours and crystallized, followed by solid phase polymerization at 220°C, a vacuum of 0.3 Torr, and 12 hours to produce masterbatch particles (MB-4-2). Table 1 shows the physical properties of the obtained masterbatch particles.

(Example 1)

After mixing 66.7 parts by mass of the masterbatch particles MB-1-1 obtained in Reference Example 1-1 and 33.3 parts by mass of PET-1, vacuum drying was carried out at a temperature of 180°C for 3 hours, and then supplied to an extruder. Under a nitrogen atmosphere, the product was melted at a temperature of 280°C and introduced into a T-die nozzle. At this time, the filter of the extruder was an 80 μm sintered filter. Next, by extruding into a sheet shape into a molten single-layer sheet in a T-die nozzle, the molten single-layer sheet was cooled and solidified on a roller maintained at a surface temperature of 25°C by an electrostatic application method. And an unstretched monolayer film is obtained.

Next, after preheating the unstretched single-layer film with a roller group heated to a temperature of 85°C, a heating roller at a temperature of 90°C is used to perform a 2.5-fold stretch in the longitudinal direction (longitudinal direction) and a roller at a temperature of 25°C. The group is cooled to obtain a uniaxially stretched film. While grasping the uniaxial extension thin with a jig Both ends of the film were guided to a preheating zone with a temperature of 80°C in a tenter, and then continuously extended 2.5 times in a direction (width direction) at right angles to the longitudinal direction in a heating zone with a temperature of 90°C. Next, heat treatment is performed at a temperature of 220° C. for 20 seconds in the heat treatment zone 1 in the tenter, heat treatment at 150° C. in the heat treatment zone 2 and heat treatment at a temperature of 100° C. in the heat treatment zone 3. Furthermore, during the heat treatment, a 4% relaxation treatment is performed between the heat treatment zone 1 and the heat treatment zone 2. Next, after gradually cooling uniformly, it was wound up to obtain a biaxially stretched film with a thickness of 50 μm.

Table 2 shows the results of evaluating the characteristics of the obtained film. It is known that the film is excellent in thermal conductivity, mechanical properties, and heat resistance.

(Examples 2 to 20)

Except that the kind and amount of the masterbatch particles used and the kind and amount of the crystalline polyester (A) are as shown in Table 2, the same operation as in Example 1 was carried out to obtain a polyester film having a thickness of 50 μm. Table 2 shows the results of evaluating the characteristics of the obtained film. It is known that the film is excellent in thermal conductivity, mechanical properties, and heat resistance. In particular, it can be seen that in Examples 4 to 7, 9 to 11, and 16 to 18, the thermal conductivity is more excellent than that of Example 1, and the thermal conductivity of Examples 11 and 16 is particularly excellent.

(Example 21)

51.7 parts by mass of masterbatch particles MB-1-2 obtained in Reference Example 1-2 and 15.0 parts by mass of masterbatch particles MB-3-4 and 33.3 parts by mass of PET-1 obtained in Reference Example 3-4 were mixed After vacuum drying at 180°C for 3 hours, it was supplied to an extruder, melted at a temperature of 280°C under a nitrogen atmosphere, and introduced into a T-die nozzle. Except this, it carried out similarly to Example 1, and obtained the polyester film of thickness 50micrometer. Table 2 shows the evaluation results The result of the properties of the film. It is known that the film is excellent in thermal conductivity, mechanical properties, and heat resistance. It can be seen that the film obtained in Example 21 is a film having better thermal conductivity than Example 19 or Example 20.

(Examples 22 to 28)

Except that the amount of the masterbatch particles used was set as shown in Table 2, the same operation as in Example 21 was carried out to obtain a polyester film having a thickness of 50 μm. Table 2 shows the results of evaluating the characteristics of the obtained film. It is known that the film is excellent in thermal conductivity, mechanical properties, and heat resistance. In particular, it can be seen that in Examples 22 to 27, the thermal conductivity is superior to Example 28, and among Examples 22 to 25, the thermal conductivity is particularly excellent.

(Comparative Examples 1~8)

Except that the type and amount of the masterbatch particles used, the type, amount and extension conditions of the crystalline polyester (A) are as shown in Table 2, the same operation as in Example 1 was carried out to obtain a polyester film with a thickness of 50 μm . Table 2 shows the results of evaluating the characteristics of the obtained film. It can be seen that Comparative Examples 1 to 3 and 5 to 8 series have poorer thermal conductivity than Example 1, and Comparative Example 4 has poor heat resistance.

In addition, the index is omitted from the table and expressed, for example, the description of 1.0E+05 indicates 1.0×10 ^-5 .

[Industry availability]

The polyester film of the present invention can provide a polyester film having better electrical insulation, thermal conductivity, and mechanical properties than conventional polyester films. The polyester film is suitable for electrical insulation materials such as copper-clad laminates, solar cell back sheets, adhesive tapes, flexible printed circuit boards, membrane switches, planar heating elements, flat cables, etc. Materials, automotive materials, and construction materials represent applications that value electrical insulation and thermal conductivity. In particular, by using the polyester film, it is possible to provide a wind power generator with high power generation efficiency, a solar cell, and an electronic device with low power consumption.

1‧‧‧Length (l)

2‧‧‧Width (b)

3‧‧‧Thickness (t)

Claims (12)

A polyester film comprising a layer (P layer) of a polyester film, the layer (P layer) containing crystalline polyester (A) and plate-like particles (b1) with an aspect ratio of 2 or more and an aspect ratio of 2 or more At least one of the needle-shaped particles (b2) has a Young's modulus of 2 GPa or more, and plate-like particles (b1) with an aspect ratio of 2 or more and needle-shaped particles (b2) with an aspect ratio of 2 or more contained in the P layer The sum of the contents is regarded as Wb (mass %), and when the porosity in the P layer is regarded as V (vol%), Wb is 10 or more, V/Wb is 1 or less, and the plate-like particles with an aspect ratio of 2 or more ( b1). The acicular particles (b2) having an aspect ratio of 2 or more have a substituent reactive with the crystalline polyester (A) on the surface (hereinafter, described as a reactive substituent (a)), and the aspect ratio The amount of the reactive substituent (a) per unit surface area of the plate-like particles (b1) of 2 or more and the needle-like particles (b2) of aspect ratio of 2 or more is 0.2×10 ^-6 mol/m ² or more 1.4×10 ^-4 mol/m ² or less. The polyester film according to claim 1, wherein the P layer contains both plate-like particles (b1) with an aspect ratio of 2 or more and needle-like particles (b2) with an aspect ratio of 2 or more, and the aspect ratio contained in the P layer When the content of plate-like particles (b1) of 2 or more is regarded as Wb1 (mass %), and the content of acicular particles (b2) with an aspect ratio of 2 or more is regarded as Wb2 (mass %), Wb2/Wb1 is 0.7 or more and 9 or less . If the polyester film of claim 1 or 2, its elongation at break is more than 10%. The polyester film according to claim 1 or 2, wherein the difference ΔTcg between the glass transition temperature Tg of the P layer and the cold crystallization peak top temperature Tcc of the P layer is 44°C or more. The polyester film according to claim 1 or 2 has a dynamic storage elastic modulus E′ of 100° C. obtained by dynamic viscoelasticity measurement at a frequency of 1 Hz (hereinafter referred to as DMA) of 5×10 ⁷ Pa or more. For the polyester film of claim 1 or 2, the thermal conductivity in the thickness direction of the film is 0.15 W/mK or more, and the surface specific resistance is 10 ¹³ Ω/□ or more. An electrically insulating sheet made of the polyester film according to any one of claims 1 to 6. A wind power generator, which is formed by using the electric insulation sheet according to claim 7. An adhesive tape made of the polyester film according to any one of claims 1 to 6. A method for manufacturing a polyester film according to any one of claims 1 to 6, characterized in that it comprises, in order: a crystalline polyester (A) and a surface having a reaction with the crystalline polyester (A) Plate-like particles (b1) having a reactive substituent (hereinafter described as a reactive substituent (a)) and an aspect ratio of 2 or more, and needle-like particles having a reactive substituent (a) on the surface and having an aspect ratio of 2 or more (b2) at least one kind of particles, a melt-kneading step of melt-kneading; a melt-extrusion step of melting a resin composition containing the crystalline polyester (A) and the particles and ejecting from a nozzle to obtain a film; biaxially rotating the film The stretching step of stretching; the amount of the reactive substituent (a) per unit surface area of the plate-like particles (b1) with an aspect ratio of 2 or more and the needle-like particles (b2) with an aspect ratio of 2 or more is 0.2×10 ^-6 mol /m ² or more 1.4×10 ^-4 mol/m ² or less. The method for manufacturing a polyester film according to claim 10, wherein the plate-like particles (b1) with an aspect ratio of 2 or more and the needle-like particles (b2) with an aspect ratio of 2 or more are subjected to a surface treatment with a reactive substituent (a) When the agent is treated, if the mass of the plate-like particles (b1) with an aspect ratio of 2 or more and the needle-like particles (b2) with an aspect ratio of 2 or more are taken as 100 parts by mass, the mass ratio of the surface treatment agent 0.1 parts by mass or more and 5 parts by mass or less. The method for manufacturing a polyester film according to claim 10 or 11, wherein after obtaining the fragment-like composition in the melt-kneading step, the obtained fragments are subjected to solid-phase polymerization, and then melt-forming is performed in the melt-extrusion step.

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